Question

A metal rod made of iron is coupled with a zinc rod in an aqueous medium. If the corrosion potential of the iron rod is -0.44 V and that of the zinc rod is -0.76 V, calculate the corrosion current density of the iron rod when coupled with the zinc rod at 25°C. The polarization resistance of the iron rod is 880 Ωcm².

Answer 1

To calculate the corrosion current density of the iron rod when coupled with the zinc rod, we can use the following equation:Corrosion current density  i_corr  =  E_corr_iron - E_corr_zinc  / R_pwhere E_corr_iron is the corrosion potential of the iron rod  -0.44 V , E_corr_zinc is the corrosion potential of the zinc rod  -0.76 V , and R_p is the polarization resistance of the iron rod  880 cm .First, we need to find the difference in corrosion potential between the iron and zinc rods:E_corr = E_corr_iron - E_corr_zinc = -0.44 V -  -0.76 V  = 0.32 VNext, we can use this value to calculate the corrosion current density:i_corr = E_corr / R_p = 0.32 V / 880 cm = 3.64  10 A/cmSo, the corrosion current density of the iron rod when coupled with the zinc rod at 25C is 3.64  10 A/cm.